Preparation of high activity catalysts; the catalysts and their use

ABSTRACT

A process for the preparation of a catalyst useful for conducting carbon monoxide hydrogenation reactions, especially a Fischer-Tropsch catalyst, use of the catalyst for conducting such reactions, especially Fischer-Tropsch reactions, and the composition produced by said process. In the preparation of the catalyst, a solution of a multi-functional carboxylic acid having from about 3 to 6 total carbon atoms, preferably about 4 to 5 total carbon atoms, is employed to impregnate and disperse a compound or salt of rhenium and a compound or salt of a catalytic metal, or metals, e.g., copper or an Iron Group metal such as iron, cobalt, or nickel onto a refractory inorganic oxide support, e.g., titania. The rhenium, which need be present only in small amount permits full and complete reduction of the catalytic metal, or metals, dispersed by the acid. Higher catalyst activities with lower rhenium loadings are thus achieved than in previous preparations where higher concentrations of rhenium were required to both effectively disperse, and reduce the catalytic metal, or metals, during the preparation. Surprisingly, as little as about 1/10 of the rhenium is required to accomplish the reduction promotion where the dispersion is effected with the acid.

This is a division of U.S. application Ser. No. 847,958 filed Apr. 22,1997, now U.S. Pat. No. 5,863,856.

FIELD OF THE INVENTION

This invention relates to a process, or method, for the production of ahigh activity catalyst by dispersion of rhenium and a catalytic metal,or metals, particularly copper or an Iron Group metal, notably cobalt,onto a refractory inorganic oxide support, notably titania; thecatalyst; its reduction, and use of the catalyst for conducting carbonmonoxide hydrogenation reactions, especially Fischer-Tropsch reactions.

BACKGROUND

Carbon monoxide hydrogenation reactions are well known. For example,Fischer-Tropsch synthesis processes, or processes for the catalyticconversion of synthesis gas, i.e., a mixture of hydrogen and carbonmonoxide, to high quality distillate fuels or mixtures of C₅ + liquidhydrocarbons are well known. For example, the Group VIII non-noblemetals, iron, cobalt, and nickel have been widely used to catalyzeFischer-Tropsch reactions, and these metals have been deposited onvarious supports, and promoted with various other metals. In U.S. Pat.No. 4,568,663, e.g., there is disclosed a process of this type whichutilizes a highly active catalyst composition constituted ofcobalt-rhenium-titania, Co--Re--TiO₂. This catalyst is made, e.g., byimpregnating a concentrated aqueous solution of cobalt nitrate andperrhenic acid onto a titania support by the conventional incipientwetness method, drying, and then calcining to decompose the nitrate saltto the oxide. Several important functions are served by the rhenium. Amajor function is served by rhenium during the calcination of thecatalyst, during which cobalt nitrate decomposes to cobalt oxide, inthat it causes the cobalt oxide to become more highly dispersed. It alsopreserves the cobalt oxide in highly dispersed state under hightemperature oxidizing conditions, such as is found useful forregenerating cobalt catalysts. It is also a function of the rhenium tolower the temperature of the reduction of cobalt oxide to the zerovalence state, which is required to achieve full activity. Rhenium makesit easier to more fully reduce the cobalt. High dispersal, and fullreduction of the cobalt results in a more active catalyst. This resulthowever does not come without cost, for rhenium is a relativelyexpensive commodity. Thus, there exists a need for means to betterdisperse the cobalt with a lesser amount of rhenium, find means forrecovering the rhenium, or find other more available, less expensivematerials for promoting the dispersion, and reduction of the metals.

In U.S. Pat. No. 1,914,557 there is disclosed the use of carboxylicacids, e.g., malic acid, as complexing agents in the preparation ofsupported metal catalysts. A solution of a "metallic-organo complex" isevaporated onto a support as an adherent sticky mass, or coating,forming a catalyst the coating of which does not readily flake or dustoff. In U.S. Pat. No. 4,409,131 there is disclosed the preparation ofsupported catalysts containing cobalt or nickel and molybdenum made byimpregnation of the support with stable solutions of cobalt or nickelcomplexed with carboxylic acid, e.g., citric acid, compatible withammonium molybdate. U.S. Pat. No. 4,568,449 discloses a process forpreparing catalysts wherein a support is premoistened in a first stepwith a carboxylic acid, and second step wherein the support isimpregnated with a solution containing molybdenum, nickel andphosphorus. In accordance with U.S. Pat. No. 4,568,450 codeposition ofmetals and carboxylic acid is made from a single solution in forming thesupported catalyst.

SUMMARY OF THE INVENTION

The present invention, which meets this and other needs, relates to anovel process for the preparation of a catalyst useful for thehydrogenation of carbon monoxide, especially a Fischer-Tropsch catalyst,the catalyst, and process for the use of this catalyst for conductingsuch reactions, especially Fischer-Tropsch synthesis reactions, i.e.,reactions for the production of C₅ + liquid hydrocarbons from hydrogenand carbon monoxide. In the preparation of the catalyst, a preformedparticulate refractory inorganic solids support, preferably titania, isimpregnated with (a) a compound, or salt, of a catalytic metal, ormetals, suitably copper or an Iron Group metal, (b) a compound, or salt,of rhenium, and (c) a multi-functional carboxylic acid. In impregnatingthe support, the support is contacted, preferably, with a singlesolution containing all of (a), (b), and (c). The multi-functionalcarboxylic acid is sufficient to distribute the compound or salt of thecatalytic metal, copper or Iron Group metal in highly dispersed form,onto the support; and, the rhenium is sufficient to produce fullreduction of the dispersed metal. Whereas rhenium has been used in thepast to produce both of these functions, a far lesser amount of rheniumis required to produce both dispersion and reduction of the metal whenthe rhenium is used in conjunction with the acid.

The multi-functional carboxylic acid is characterized as having theformula

    HOOC--(CRR.sup.1).sub.n --COOH

wherein n is an integer defining the length of the chain of carbon atomsbetween the two terminal carboxylic acid groups and is equal to orgreater than 1 and can range as high as about 4, and preferably n rangesfrom about 2 to about 3; and substituents R and R¹ are the same ordifferent, and are selected from the group consisting of hydrogen,hydrocarbyl, i.e., hydrocarbon groups per se, or hydrocarbon groupswhich contain oxygen, nitrogen, or the like, suitably alkyl, e.g.,methyl, ethyl, propyl, etc., hydroxyl, carboxyl, amino, alkoxy and thelike. Malonic acid, aspartic acid, tartaric acid, succinic acid, citricacid, glutaric acid, glutamic acid, adipic acid, and the like areexemplary of these multi-functional carboxylic acids.

It has been found that the copper or Iron Group metal can be moreeffectively dispersed onto the support via use of the multi-functionalcarboxylic acid than with rhenium, as a consequence of which no rheniumis required to effect a full, and complete dispersion of the catalyticmetal, or metals. However, some rhenium is required since its presenceenables a more complete and full reduction of the dispersed copper orIron Group metal to the zero valent state. Accordingly, in the practiceof this invention, a small amount of a compound or salt of rhenium, andboth a compound or salt of copper or an Iron Group metal and amulti-functional carboxylic acid, are employed to disperse the copper orIron Group metal, and rhenium, onto the solids support component of thecatalyst during the impregnation; dispersion of the copper or Iron Groupmetal into the preformed catalyst resulting from the presence ofmulti-functional carboxylic acid, while the rhenium is effective inpermitting full reduction of the catalyst after calcination. The copperor Iron Group metal compound, and rhenium compound, are thus effectivelydispersed during the impregnation step, and during calcination themulti-functional carboxylic acid is removed by combustion leaving behindcrystallites of well dispersed oxides of the copper or Iron Group metaland the rhenium. Essentially complete reduction of the crystallites ofthe metals is achieved on contact of the calcined catalyst with areducing agent, e.g., hydrogen. Surprisingly, in the preparation of acatalyst it is found that considerably less rhenium is required overallwhen prepared with a multi-functional carboxylic acid to produce a full,similar level of activity in a reduced copper or Iron Groupmetal/rhenium catalyst of given composition, used in a carbon monoxidehydrogenation or Fischer-Tropsch reaction, than with a reduced catalystof corresponding composition, used in a similar carbon monoxidehydrogenation or Fischer-Tropsch reaction at similar process conditions,made in a preparation otherwise similar except that the catalyst wasmade without use of a multi-functional carboxylic acid.

DETAILED DESCRIPTION

The catalysts are formed by deposition of the catalytic metal, ormetals, on a previously pilled, pelleted, beaded, extruded, spray dried,or sieved support material by the impregnation method. In preparing thecatalysts, the metals are deposited from solution on the support inpreselected amounts to provide the desired absolute amounts, and weightratios of the metals being deposited. Catalysts constituted of cobaltand rhenium supported on titania, or a titania-containing support, withor without the addition of an additional metal, or metals, promoter ormodifier, e.g., ruthenium, hafnium, zirconium, titanium, chromium,thoria, copper, etc., exhibit superior hydrocarbon synthesischaracteristics and provide high selectivities in the conversion ofsynthesis gas to C₅ + hydrocarbon liquids. Suitably, the metals arecodeposited by contact and treatment of the support with a solution,suitably an aqueous solution, which contains the multi-functionalcarboxylic acid, e.g., glutamic acid, in addition to the compound orsalt of the copper or Iron Group metal, e.g., cobalt, or the compound orsalt of the rhenium, or both the compound or salt of the copper or IronGroup metal and the compound or salt of the rhenium.

The catalytic metal, copper or Iron Group metal, and the rhenium can bedeposited from solution in sequence, or codeposited from the sameimpregnating solution, and the multi-functional carboxylic acid can bedeposited from solution in sequence with the copper or Iron Group metal,and rhenium, or codeposited with the copper or Iron Group metal and therhenium. The multi-functional carboxylic acid can thus be codepositedwith a catalytic metal, or metals, or it can be deposited from solutionby a separate impregnation. Preferably however, the multi-functionalcarboxylic acid is codeposited with the copper or Iron Group metal andthe rhenium. The volume of impregnating solution used in an impregnationusually ranges from about 1 to about 20 times the volume of the support,and is generally carried out at ambient or elevated temperature.Preferably, the impregnation is carried out at conditions of incipientwetness, and at essentially ambient temperature. In accordance with theincipient wetness technique, as is known, the volume of the impregnatingsolution and amount of metals is predetermined to correspond to themaximum volume which will just fill the internal pore volume of thesupport, with no liquid in excess on impregnation of the support.Various refractory inorganic oxide supports are useful in the formationof catalysts pursuant to the practice of this invention. Exemplary ofsuch supports are titania, which is preferred, silica, silica-alumina,alumina, and the like.

Highly concentrated metal salt solutions are most desirable forpreparing hydrocarbon synthesis catalysts because they generate thehighest metal loading per impregnation, higher metal loadings leading inturn to higher catalytic activity. Common salts or compounds of thecatalytic metals can generally be used. However, it has been found thatthe nitrate salt, especially in the case of cobalt is preferred becauseit is the most readily available and least expensive salt and, moreimportantly, it possesses the highest degree of solubility in water.Cobalt acetate is also suitable, although it is less water soluble.Cobalt chloride and sulfate are not suitable for making hydrocarbonsynthesis catalysts, presumably because of poisoning by residual anionsnot removed in the calcination, regardless of the promotion ofdispersion by multi-functional carboxylic acids. Solvents other thanwater may be used, like alcohols, ketones and the like, but aregenerally not preferred because of lower metal salt solubility and addedmanufacturing cost. Suitable rhenium compounds are the common watersoluble ones, especially perrhenic acid and ammonium perrhenate.

The catalytic metal, copper or Iron Group metal, preferably cobalt, isadded to the support in amount sufficient to provide from about 2percent to about 50 percent, preferably from about 5 percent to about 35percent of the elemental metal, based on the total weight of thefinished catalyst (dry basis). The maximum metal loading that can beobtained per impregnation will depend upon the support pore volume,which will in turn depend upon the support composition, and the metalconcentration in the impregnating solution. Multipleimpregnation/calcination steps may be used to obtain high final metalloadings. Other metals, e.g., thorium, cerium, hafnium, uranium and thelike can be added if desired to modify or promote the activity of thefinished catalyst. These metals when present are added in weight ratioto copper or Iron Group metal ranging above about 0.01:1, preferablyfrom about 0.025:1 to about 0.1:1. Rhenium is added to the support inconcentration sufficient to provide a weight ratio of elementalrhenium:elemental copper or Iron Group metal (e.g., Re/Co weight ratio)in the finished catalyst ranging from about 0.005:1 to about 0.2:1,preferably from about 0.01:1 to about 0.1:1 (dry basis). Themulti-functional carboxylic acid is added to the support inconcentration sufficient to disperse the copper or Iron Group metalcompound throughout the support, from about 2 percent to about 30percent, preferably from about 6 percent to about 25 percent, of themulti-functional carboxylic acid generally being adequate to fullyaccomplish this objective; and it does this even more effectively thanthe rhenium. Preferably, the multi-functional carboxylic acid is addedto metal salt impregnating solution such that the mole ratio of thecarboxylic acid compound to metal is about 0.1:1 to about 0.6:1,preferably from about 0.2:1 to about 0.5:1. The catalyst, afterimpregnation, is dried by heating, suitably at temperatures ranging fromabout 30° C. to about 120° C., in an air, nitrogen or other gas streamor under vacuum. The metals are converted to an oxide form bycalcination, suitably at temperature ranging from about 200° C. to about550° C., preferably from about 250° C. to about 400° C., and themulti-functional carboxylic acid is burned, combusted, and removed fromthe catalyst. The catalyst is then activated by reduction, suitably bycontact with hydrogen at temperature ranging from about 250° C. to about550° C., preferably from about 275° C. to about 425° C., for periodsranging from about 0.5 hour to about 24 hours at pressures ranging fromabove ambient to about 40 atmospheres.

The catalyst produced in accordance with this invention, particularlythose comprised of the Iron Group metals, corresponds in composition tothose known, and useful in the conversion of synthesis gas to waxy,paraffinic C₅ + hydrocarbons. The Fischer-Tropsch, F-T, or hydrocarbonsynthesis process is carried out at temperatures of about 160° C. toabout 325° C., preferably from about 190° C. to about 260° C., pressuresof about 5 atm to about 100 atm, preferably about 10-40 atm and gashourly space velocities of from about 300 V/Hr/V to about 20,000 V/Hr/V,preferably from about 500 V/Hr/V to about 15,000 V/Hr/V. Thestoichiometric ratio of hydrogen to carbon monoxide in the synthesis gasis about 2.1:1 for the production of higher hydrocarbons. However, H₂/CO ratios of 1:1 to about 4:1, preferably about 1.5:1 to about 2.5:1,more preferably about 1.8:1 to about 2.2:1 can be employed. Thesereaction conditions are well known and a particular set of reactionconditions can be readily determined by those skilled in the art. Thereaction may be carried out in virtually any type reactor, e.g., fixedbed, moving bed, fluidized bed, slurry, bubbling bed, etc. The waxy, orparaffinic product from the F-T reactor, or reactor utilizing thecatalyst made pursuant to the practice of this invention is anessentially non-sulfur, non-nitrogen, non-aromatics containinghydrocarbon. It is a liquid product which can be produced and shippedfrom a remote area to a refinery site for further chemically reactingand upgrading to a variety of products, or produced and upgraded at arefinery site. Separator products taken from the F-T reactor, i.e., hotseparator and cold separator liquids, respectively, i.e., C₄ -C₁₅hydrocarbons, constitute high quality paraffin solvents which, ifdesired, can be hydrotreated to remove olefin impurities, or employedwithout hydrotreating to produce a wide variety of non-toxic waxproducts. The reactor wax, or C₁₆ + liquid hydrocarbons from the F-Treactor, on the other hand, can be upgraded by various hydroconversionreactions, e.g., hydrocracking, hydroisomerization catalytic dewaxing,isodewaxing, etc., or combinations thereof, to produce such products asstable, environmentally benign, non-toxic mid-distillates, diesel andjet fuels, e.g., low freeze point jet fuel, high cetane jet fuel etc.,isoparaffinic solvents, lubricants, e.g., lube oil blending componentsand lube oil base stocks suitable for transportation vehicles, non-toxicdrilling oils suitable for use in drilling muds, technical and medicinalgrade white oils, chemical raw materials and various specialty products.

The following non-limiting examples, and comparative demonstrations,exemplify the more salient and preferred embodiments of the invention.

EXAMPLES

A series of catalysts were prepared by impregnating a support, generallya rutile or anatase titania support, but including alumina and silica,with a concentrated aqueous solution of cobalt nitrate and perrhenicacid via the incipient wetness technique. In most of the preparations,as tabulated hereafter, different multi-functional carboxylic acids weredissolved in cobalt nitrate/perrhenic acid solutions, themulti-functional carboxylic acid generally being added in concentrationof 0.306 mole per mole of elemental cobalt. The amount of water presentin each impregnating solution was adjusted for the weight of the acidadded to maintain a constant 15 wt. % cobalt, calculated as elementalcobalt, in the solution. In a base case preparation, for comparativepurposes, no multi-functional carboxylic acid was added to the cobaltnitrate/perrhenic acid solution. In some cases the catalysts were madeby single impregnations (about 7 wt. % Co in the finished catalysts) inthe exploration of preparation variables. In other cases, a secondimpregnation was applied to increase metals loadings and producefinished catalysts more typical of those which may be employed in largescale operations. In each preparation, after impregnation the catalystwas dried and then calcined in air to decompose the nitrate salt to theoxide and burn off the organic additive.

Most of the preps were made with a spray-dried titania support. Twobatches were used which were obtained by calcining the raw spray-driedsupport at two different temperatures, as indicated in the followingtable. An extruded alumina support ground to 63-125 micron size and aspray-dried silica support were also used in a few examples.

    ______________________________________                                                  Calcination Surface Area                                                                            H.sub.2 O Pore                                Designation                                                                             Temp. ° C.                                                                         m.sup.2 /g                                                                              Volume, cc/g                                  ______________________________________                                        Rutile.sup.(1)                                                                          1000        19        0.33                                          Anatase.sup.(2)                                                                         500         29        0.50                                          Alumina   540         189       0.48                                          Silica    800         170       1.02                                          ______________________________________                                         .sup.(1) 94% Rutile  6% Anatase TiO.sub.2                                     .sup.(2) 27% Rutile  73% Anatase TiO.sub.2                               

Each of the catalysts were characterized by the following tests.

O₂ Chemisorption: measured with O₂ pulses in helium at 25° C. afterreduction in hydrogen at 450° C. Results are expressed as micromoles O₂per gram and as an O/Co atomic ratio. The oxygen chemisorption is ameasure of the relative dispersion of cobalt oxide on the support.

Fixed Bed Hydrocarbon Synthesis (HCS) Test: conducted at 200° C., 280psig, with a syn gas feed of 65H₂ -31CO-4Ne and GHSV adjusted asrequired to give conversion around 70% at 16-20 hours on stream.Catalysts were diluted with 1-7 parts by volume of titania to minimizetemperature gradients in a 0.25 inch ID reactor, used to conduct thetest. Prior to introducing the syn gas, the catalyst is reduced in situin hydrogen for one hour at the temperature shown in the Tables.Conversion of CO and selectivity to methane (mole % of CO converted toCH₄) are shown in the Tables. Values for "Cobalt Productivity," whichhas the units of liters of CO converted per hour per gram of cobalt, arealso included in each of the Tables.

Table 1: Effect of Multi-Functional Carboxylic Acid Composition

Table 1 summarizes the results obtained with different multi-functionalcarboxylic acids as impregnation aids for dispersing the cobaltthroughout a support. The examples were made with the rutile titaniasupport, without any rhenium promoter. The key results are given in thelast column, i.e., reference being made to the O/Co chemisorption data.The catalysts are grouped according to the length of the longest carbonchain in the organic acid. Example 1 demonstrates for comparativepurposes a run made without use of any multi-functional carboxylic acidin the preparation. Examples 2-7 show minimal improvement when thecatalysts are produced by dispersion of the cobalt with 3Cmulti-functional carboxylic acids. In Examples 8-14, on the other hand,wherein 4C to 6C multi-functional carboxylic acids were used in thepreparations, higher relative dispersions were obtained. These acidsgive an O/Co over 0.4 compared to a value of less than 0.3 for the basecase. From a list of the structures of the acids tested, the criticalstructural features of the preferred acids are shown to have a totalcarbon chain of at least four atoms, preferably 5 atoms. Themulti-functional carboxylic acids, it is believed, improve cobaltdispersion by covering the titania surface with a thin "blanket" of theacid, which provides a trap for molten anhydrous cobalt nitrate as it isgenerated in the pores during the drying/calcination process. In theabsence of something so polar to bind to, the cobalt salt probablycoalesces into larger crystallites as it decomposes to the oxide. Thepreference for the longer chain length is especially significant;noting, e.g., how relatively ineffective a shorter chain is, likemalonic acid. This longer chain, it is believed, does not chelate to asingle species, but rather attaches itself to two entities, the cobalton one end and the titania on the other. There appears no evidence ofcomplexation between either glutamic or citric acid and the Co+2 in thestarting solution by UV spectroscopy, though complexation may occurlater as the mixture is heated and dried in the calcination process.This is fortunate because preformed complexes appear to be much lesssoluble, and hence would perform poorly in the very concentratedsolutions as used herein.

The Cobalt Productivity values for Examples 1-14, it will be observed,fail to show a significant activity credit despite the improved cobaltdispersion. The problem lies in achieving full reduction of the improveddispersion; a problem solved by including a small amount of rhenium asreduction promotor as subsequently illustrated.

Comparison of Example 15 with Examples 16 and 17 illustrates that thedispersion advantage seen for the two best multi-functional carboxylicacids, glutamic acid and citric acid, is also present after a secondimpregnation is applied to achieve higher cobalt loading. As will beobserved, the reducibility problem however is dampened somewhat by thehigher metal loading (it is easier to reduce 12% Co than 7% Co), so anactivity credit is observed to augment the dispersion credit. Example 16represents a very active Re-free Co--TiO₂ catalyst.

Table 2: Effect of Multi-Functional Carboxylic Acid Loading

The molar ratio of the multi-functional carboxylic acid to elementalcobalt was varied with glutamic acid, citric acid, and tartaric acid, asshown by Examples 18-29, summarized in Table 2. It is clear from thesedata that an optimum ratio exists between about 0.2 and about 0.5, withthe best dispersion credit occurring at about 0.3 mole of acid per moleof cobalt for all three acids. Preference for this ratio may reflectmore the ratio of the acid to the support surface area rather than tothe cobalt (these ratios are proportional to each other in most of thesepreps). For example, the larger concentrations of acid may be lesseffective because the "blanket" is getting too thick, supra. The optimumacid:Co ratio may thus be a function of the support surface area.

Table 3: Effect of Rhenium

The incorporation of some rhenium permits maximization of thehydrocarbon synthesis activity of the catalyst. The acids functionextremely well in generating cobalt dispersion, but the activity of thecatalyst does not correspondingly increase unless the reducibility ofthe dispersed cobalt oxide to the active zero-valent state is improved.Simply applying higher temperature in the reduction step does not solvethe problem because the growth of a titania overlayer with titania, orsintering of the cobalt metal in the case of alumina or silica, areprocesses that are favored by higher temperature and counteract anypositive gains in reduction. The addition of some rhenium howevergreatly improved the extent of cobalt oxide reducibility at 300-450° C.Examples 30-34 of Table 3, base case examples not of this invention,show that activity gradually increases with Re:Co ratios up to about0.09, but there is no further improvement in activity at higher Re:Coratios. Examples 35-39, on the other hand wherein glutamic acid is usedto promote dispersion on the base case rutile support, show a rapidincrease in activity as rhenium is introduced into these glutamic preps.Cobalt Productivity over 5, which is higher than the best of the basecase catalysts, is achieved with only a 0.01 Re:Co ratio. Examples 40-45show similar findings with the higher pore volume, anatase form of thesupport. Here activity also increases dramatically with rhenium, with anoptimum ratio occurring at about 0.04, which is half the base caseoptimum.

While Cobalt Productivity is very useful in assessing cobalteffectiveness in the hydrocarbon conversion reaction, WeightProductivity is the activity measure that best defines the relativeperformance of a catalyst in a slurry reactor. Weight Productivityresults (cc CO converted per hour per gram of catalyst) for Examples30-45 show that the higher metal loading obtained with the higher porevolume, anatase support adds significantly to the advantage gained withthe glutamic-low rhenium recipe to generate higher activity catalysts.Comparison of the catalyst of Example 45, with half the base case Re:Coratio, is twice as active as the catalyst of base case Example 34.

Table 4: Other Metals and Supports

Table 4 provides Examples 46-49 showing that dispersion improvement withglutamic acid occurs with other Group VIII metals besides cobalt, e.g.,copper and nickel. Examples 50-54 show that glutamic and citric acidsimprove cobalt dispersion on alumina, with or without added rhenium.Examples 55-56 show that glutamic acid improves cobalt dispersion on asilica support. Solutions as concentrated as possible at roomtemperature were used in these preps. In the Examples using organicacids, the mole ratio of the organic acid to cobalt in the impregnatingsolution was 0.3.

                                      TABLE 1                                     __________________________________________________________________________    Effect of Multi-Functional Carboxylic Acid Compositions                            Multi-Functional                                                              Carboxylic Acid                                                                        Wt. %                                                                             H.sub.2         Mol %                                                                             Co                                      Example                                                                            (Acid/Co = 0.306)                                                                      Co  Temp                                                                             Density                                                                           GHSV                                                                              CO Conv                                                                            CH.sub.4                                                                          Prod                                                                             Chemis                                                                            O/Co                             __________________________________________________________________________    Single Impregnations:                                                         1    none     7.06                                                                              450                                                                              1.13                                                                              875 70   5.1 2.46                                                                             165 0.276                            2    glycine  6.99                                                                              450                                                                              1.08                                                                              750 68   5.0 2.16                                                                             222 0.375                            3    alanine  6.81                                                                              450                                                                              1.08                                                                              850 67   5.2 2.48                                                                             184 0.319                            4    leucine  7.06                                                                              450                                                                              1.08                                                                              875 76   4.3 2.79                                                                             211 0.353                            5    serine   6.85                                                                              450                                                                              1.08                                                                              900 70   5.0 2.73                                                                             224 0.386                            6    threonine                                                                              7.23                                                                              450                                                                              1.08                                                                              900 77   4.5 2.84                                                                             241 0.393                            7    malonic acid                                                                           7.15                                                                              450                                                                              1.08                                                                              625 71   4.6 1.84                                                                             182 0.300                            8    tartaric acid                                                                          6.75                                                                              450                                                                              1.08                                                                              800 67   5.0 2.35                                                                             268 0.469                            9    aspartic acid                                                                          7.00                                                                              450                                                                              1.08                                                                              850 68   5.1 2.45                                                                             253 0.426                            10   succinic acid                                                                          5.53                                                                              450                                                                              1.08                                                                              750 72   5.0 2.89                                                                             218 0.465                            11   citric acid                                                                            7.10                                                                              450                                                                              1.08                                                                              850 71   5.1 2.52                                                                             336 0.558                            12   glutamic acid                                                                          7.39                                                                              450                                                                              1.08                                                                              1150                                                                              74   4.2 3.41                                                                             345 0.551                            13   glutaric acid                                                                          7.15                       268 0.442                            14   adipic acid                                                                            5.41                                                                              450                                                                              1.08                                                                              650 71   5.7 2.53                                                                             204 0.455                            Double Impregnations:                                                         15   none     12.65                                                                             450                                                                              1.37                                                                              1400                                                                              72   4.6 1.86                                                                             239 0.223                            16   glutamic acid                                                                          12.07                                                                             450                                                                              1.37                                                                              2800                                                                              64   5.3 3.47                                                                             475 0.464                            17   citric acid                                                                            12.87                                                                             450                                                                              3.37                                                                              2200                                                                              70   4.8 2.79                                                                             411 0.377                            __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    Effect of Multi-Functional Carboxylic Acid Loading                                 Acid/Co mol                                                                         Wt. %                                                                             H.sub.2         Mol %                                                                             Co                                         Example                                                                            ratio Co  Temp                                                                             Density                                                                           GHSV                                                                              CO Conv                                                                            CH.sub.4                                                                          Prod                                                                             Chemis                                                                            O/Co                                __________________________________________________________________________    Glutamic Acid                                                                 18   0.102 6.71                                                                              450                                                                              1.08                                                                              750 67   5.0 2.22                                                                             173 0.304                               19   0.204 7.14                                                                              450                                                                              1.08                                                                              875 70   5.1 2.54                                                                             262 0.433                               20   0.306 7.39                                                                              450                                                                              1.08                                                                              1150                                                                              74   4.2 3.41                                                                             345 0.551                               Citric Acid                                                                   21   0.102 7.08                       121 0.202                               22   0.204 7.20                       182 0.298                               23   0.306 7.10                                                                              450                                                                              1.08                                                                              850 71   5.1 2.52                                                                             336 0.558                               24   0.502 6.58                       271 0.486                               25   1.15  6.71                       191 0.336                               Tartaric Acid                                                                 26   0.191 7.42                       219 0.348                               27   0.306 6.75                                                                              450                                                                              1.08                                                                              800 67   5   2.35                                                                             268 0.469                               28   0.408 7.52                       244 0.383                               29   0.549 6.3                        185 0.347                               __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Effect of Rhenium                                                                  Wt. %                                                                             Wt. %   H.sub.2    Co Mol %                                          Example                                                                            Co  Re  Re/Co                                                                             Temp                                                                             Density                                                                           GHSV                                                                              Conv                                                                             CH.sub.4                                                                          Chemis                                                                            O/Co                                                                             Co Prod                             __________________________________________________________________________    Base Case On Rutile Support Without Multi-functional Carboxylic Acid          30   11.72                                                                             0   0   375                                                                              1.43                                                                              1750                                                                              73 5   243 0.245                                                                            2.44                                31   12.12                                                                             0.139                                                                             0.0115                                                                            375                                                                              1.43                                                                              2000                                                                              70 5.1 336 0.327                                                                            2.59                                32   11.79                                                                             0.252                                                                             0.0214                                                                            375                                                                              1.43                                                                              2500                                                                              73 5.5 360 0.360                                                                            3.46                                33   11.79                                                                             0.697                                                                             0.0591                                                                            375                                                                              1.43                                                                              3000                                                                              73 5.7 394 0.394                                                                            4.16                                34   11.32                                                                             1.07                                                                              0.0945                                                                            375                                                                              1.43                                                                              3500                                                                              73 5.9 395 0.412                                                                            5.05                                Glutamic Acid Used With Rutile Support                                        35   12.07                                                                             0   0   450                                                                              1.37                                                                              2800                                                                              64 5.8 475 0.464                                                                            3.47                                36   12.84                                                                             0.049                                                                             0.0039                                                                            450                                                                              1.37                                                                              3500                                                                              73 4.7 545 0.501                                                                            4.65                                37   11.16                                                                             0.108                                                                             0.0097                                                                            450                                                                              1.37                                                                              3600                                                                              73 5.1 562 0.594                                                                            5.50                                38   12.59                                                                             0.509                                                                             0.0404                                                                            450                                                                              1.37                                                                              4000                                                                              70 5.5 636 0.596                                                                            5.19                                39   12.22                                                                             1.093                                                                             0.0894                                                                            450                                                                              1.37                                                                              4000                                                                              71 5.5 683 0.660                                                                            5.43                                Glutamic Acid Used With Anatase Support                                       40   16.92                                                                             0   0   450                                                                              1.23                                                                              1400                                                                              73 4.6 415 0.289                                                                            1.57                                41   16.08                                                                             0.061                                                                             0.0038                                                                            450                                                                              1.23                                                                              2200                                                                              72 5   516 0.379                                                                            2.56                                42   17.27                                                                             0.128                                                                             0.0074                                                                            375                                                                              1.23                                                                              3800                                                                              68 4.5 588 0.402                                                                            3.89                                43   16.72                                                                             0.327                                                                             0.0196                                                                            375                                                                              1.23                                                                              5500                                                                              67 5.1 702 0.495                                                                            5.73                                44   16.52                                                                             0.649                                                                             0.0393                                                                            375                                                                              1.23                                                                              5500                                                                              69 4.8 691 0.494                                                                            5.98                                45   16.44                                                                             1.472                                                                             0.0895                                                                            375                                                                              1.23                                                                              5600                                                                              70 5.7 900 0.646                                                                            6.20                                __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Other Metals and Supports                                                                 Multi-Functional                                                  Example                                                                            Support                                                                              Carboxylic Acid                                                                       Wt % Co                                                                            Wt % Cu                                                                            Wt % Ni                                                                            Wt % Re                                                                            Chemis                                __________________________________________________________________________    46   TiO.sub.2 (Rutile)                                                                   none    0    8.4  0    0    14                                    47   TiO.sub.2 (Rutile)                                                                   glutamic acid                                                                         0    8.8  0    0    86                                    48   TiO.sub.2 (Anatase)                                                                  none    0    0    10   0    167                                   49   TiO.sub.2 (Anatase)                                                                  glutamic acid                                                                         0    0    10   0    223                                   50   Al.sub.2 O.sub.3                                                                     none    16.6 0    0    0    329                                   51   Al.sub.2 O.sub.3                                                                     glutamic acid                                                                         16.6 0    0    0    653                                   52   Al.sub.2 O.sub.3                                                                     citric acid                                                                           16.6 0    0    0    599                                   53   Al.sub.2 O.sub.3                                                                     none    16.6 0    0    1.4  1002                                  54   Al.sub.2 O.sub.3                                                                     glutamic acid                                                                         16.6 0    0    1.4  1570                                  55   SiO.sub.2                                                                            none    17.4 0    0    0.77 776                                   56   SiO.sub.2                                                                            glutamic acid                                                                         18.1 0    0    0.80 1576                                  __________________________________________________________________________

Additional runs were made with malic acid, a 4C chain dicarboxylic acidwith a hydroxyl group on the second carbon; one wherein a titaniasupport was contacted and impregnated with a solution of malic acid andcobalt nitrate and a second by forming a cobalt metal complex withcobalt nitrate in water and sodium hydroxide, and heating as describedby Example 13 of U.S. Pat. No. 1,914,557.

First, a catalyst was prepared by the incipient wetness technique as inthe foregoing; a solution containing cobalt nitrate and malic acid, in amole ratio of acid:Co=0.3, being impregnated from aqueous solution intoa rutile titania support as described by Examples 1-14, with thefollowing results:

    ______________________________________                                                  Multi-Functional                                                    Example   Carboxylic Acid                                                                           Wt. % Co.  Chemis                                                                              O/Co                                   ______________________________________                                        57        Malic acid  7.06       297   0.496                                  ______________________________________                                    

As indicated by the chemisorption data, malic acid behaves in thisprocedure much like other 4C acids, i.e., like tartaric and succinic.Thus, used in this procedure there is a consistent relationship betweenthe acid structure, notably carbon chain length, and the promotion ofcobalt dispersion.

Quite different from the impregnation, or incipient wetness procedure,the Patentee makes a solution of the metal complex and then evaporatesthis solution onto a support. Using Example 13 of the patent as a guide,a catalyst was made according to the following:

11.55 grams of cobalt nitrate [Co(NO₃)₂ -6H₂ O] was dissolved in 100 mlH₂ O. 3.29 grams of NaOH was dissolved in 50 ml H₂ O and added slowly tothe stirred cobalt nitrate solution. The resulting precipitate of cobalthydroxide was filtered through a Buchner funnel and washed with 50 ml ofH₂ O. All of the wet precipitate (9.9 grams) was added to a solution of5.5 grams malic acid in 75 ml H₂ O. A dark violet solution formed aftersonicating for about 10 minutes at 50° C. Some light pink solid remainedundissolved. The solution containing the cobalt malate complex wasdecanted into a flask containing 30.0 grams of the rutile titaniasupport. The solution was then evaporated onto the support with a rotaryevaporator. The impregnated catalyst was calcined in the quartz reactortube with an air flow of 375 cc/min at 300° C. for 3 hours. The finishedcatalyst was found to contain 5.47 wt % Co, which is lower than the 7%target because of the incomplete dissolution of the cobalt hydroxide inthe presence of the malic acid. Oxygen chemisorption was 93 micromoles02/gram, which corresponds to an O:Co ratio of 0.201.

This prep was thus found to be significantly inferior to those madeaccording to the incipient wetness procedure, supra. Cobalt dispersionas measured by the relative oxygen chemisorption is especially poor,only 0.201 O/Co versus 0.496 in the preceding example. Thus, there is adisadvantage in forming the cobalt-acid complex as opposed to a simplemixture of the nitrate salt and the acid. Furthermore, there is thedisadvantage of lower solubility of the complex compared to the nitratesalt and acid mixture. As indicated by this test, it is not possible toobtain a 15 wt % Co concentration in the impregnating solutions, as isdone in the method of this invention. Even as little as 3 wt % Co wouldnot dissolve. Lower cobalt solubility means less cobalt loading perimpregnation, which will translate to a significant debit in thecatalyst manufacturing cost, if viable at all.

Spectroscopic evidence suggests that complex formation between thecobalt and the di-acid does not occur at all in an impregnating solutionas practiced in accordance with the present invention; even if some kindof complex formed in-situ, during the drying of the impregnatedcatalyst. In accordance with the practice of this invention, some typeof binding with the support surface area may occur thereby providing avery polar "blanket" which favors a better dispersion of the cobaltnitrate salt, right before it decomposes. This theory rationalizes thepreference for the five-carbon acids: the best dispersion promotersbeing those acids which are long enough to disfavor bonding both ends tothe cobalt but rather favor bonding to cobalt with one end and to thesupport with the other.

Complete reduction of the catalytic metal, or metals, is required toachieve full catalyst activity. Full catalyst activity however can beachieved by only a small amount of rhenium, even at lower reductiontemperatures. Surprisingly, as little as 1/10 of the base case amount ofrhenium will satisfactorily promote the reduction when the dispersion isaccomplished by the presence of the acid. Activity with this smallamount of rhenium is generally about 20% higher than in the base,whereas it is about 20% lower without the rhenium. It therefore becomespossible with the copresence of the acid to make drastic reductions inthe amount of rhenium employed while yet achieving full dispersion andreduction of the catalyst.

What is claimed is:
 1. A process for the production of C₅ + liquidhydrocarbons from a hydrogen and carbon monoxide synthesis gas bycontacting the synthesis gas with a catalyst prepared by impregnating arefractory inorganic support with a solution containing (a) a compoundor a salt of a catalytic metal and (b) a multifunctional carboxylic acidhaving the formula

    HOOC--(CRR.sup.1).sub.n --COOH

where n is an integer from 1-4, R and R¹ are the same or different andare selected from the group consisting of hydrogen, hydrocarbyl,hydroxyl, carboxyl, amino and alkoxy, and sufficient to disperse thecompound or salt of the catalytic metal onto the support, and (c) acompound or salt of rhenium, and drying and removing themulti-functional carboxylic acid, forming oxides of the metals on thesupport, and activating the catalyst.
 2. The process of claim 1 whereinthe catalytic metal is cobalt.
 3. The process of claim 2 wherein atleast a portion of the C₅ + liquid hydrocarbon is subjected toconversion.
 4. The process of claim 3 wherein the conversion ishydroconversion.
 5. The process of claim 4 wherein the hydroconversionis hydroisomerization.
 6. The process of claim 5 wherein diesel fuelsare produced.
 7. The process of claim 5 wherein jet fuels are produced.8. The process of claim 5 wherein the hydroconversion is catalyticdewaxing.
 9. The process of claim 8 wherein lube oil base stocks areproduced.